The present invention relates to a safety ski binding with a plate pivotally mounted on the ski adapted to receive the ski boot, and with swivelling, spring-mounted holding elements with directional release characteristics.
Such a safety ski binding secures the ski boot to the ski and releases the boot in case of falls, overcoming the release forces predetermined by the release characteristics of the holding elements. The conditions for such a safety ski binding are determined by the ski's leverage on the leg.
In the known binding systems, the ski boot is generally secured to the ski by means of a toe iron and a heel element, with the toe iron releasing the boot upon occurrence of excessive torsional loads, and the heel element in case of forward falls.
In safety ski bindings of this kind, the toe iron and the heel element are permanently joined to the ski. This two-point attachment and two-point release has disadvantages, which are accounted for as follows:
Since the distance between these two holding elements changes with the bending of the ski, the constancy of the release sequence is not insured with the predetermined setting as a result of the varying influence exerted on the two holding elements.
It has also been tried to achieve an improvement by using a plate which receives the boot and is pivotally mounted on the ski. This results in a slightly better constancy of the set release values, but the disadvantages of the two-point attachment and of the two-point release remain; they are mainly due to the use of a toe iron.
The torque of the ski is transmitted via the toe iron and via the heel element to the leg. At these two points of application, the point of the foot and the heel, however, the leg, according to the principle of the lever, can be twisted by a minimum force applied thereto, in which case the torsional movements initiated via the point of the foot because of the long lever from the point of the foot to the leg's axis of rotation may be especially harmful to the leg.
The toe iron, therefore, requires a precise setting of the point of release. However, this precise setting of the toe iron is rendered difficult by the fact that the following factors must be considered: height of the skier, fone frame, skiing ability, boot size, boot material, boot stiffness, sole quality, sole stiffness. Thus, the great number of these variables and the deformation of the ski boot between the binding elements in case of the ski being bent through will easily result in a false setting of the toe iron's point of release.
In addition, considering the anatomy of the foot, it is wrong to choose the front of the boot as the point to which the torque releasing the ski upon occurrence of an excessive torsional stress is applied. The front portion of the foot and the anklebone form the upper ankle joint, i.e. an angle joint, while the heel bone and the anklebone constitute the swivel joint of the foot.
It is the object of the present invention to design a safety ski binding of the kind referred to by way of introduction in such a manner that the set release values can be kept virtually constant and also independent of deflections of the ski, avoiding, as far as possible, forces due to lever action, and that, in case of falls, the transmission of the release forces to the holding element can be effected without the leg being subjected to the aforementioned detrimental stresses.